It is very interesting. I worked in restaurants for many years and I never knew a server who made less than the back staff - usually they made several multiples of their pay in a night.
I assume it's because servers (and I was one!) feel generally more empowered when it comes to their pay; they think complaining will accomplish something (strengthen social norms to tip), while kitchen staff know that what they get is what they get.
No doubt server pay varies wildly, but I worked at a cheap buffet essentially just bussing tables and I never made less than kitchen staff and sometimes made up to 6x what they would make in a shift - usually about 3x, and management directed that we report the minimum amount possible, to get out of their payroll tax contribution, I assume.
On top of that, employers are in fact nominally required to pay the difference between their tipped wage and the "real" minimum wage if they don't get enough tips (for some reason this isn't commonly known) to make the difference, but that situation is probably rare enough that businesses skate by without fulfilling their legal duty. [1]
Frankly, I liked waiting tables and I'd do it again if it paid as much as programming. It's not all that crappy. :) And at the same time, I have a lot less sympathy for servers than I used to. Save your sympathy for the people who are paid minimum wage and don't get tips. Yes, that server is getting $2.15 instead of $7.25, but a) the business is required to make up the difference between $2.15 + tips and $7.25 and b) no server I have ever heard of, anywhere, is making less than $7.25/hour with tips.
[1] https://www.dol.gov/general/topic/wages/wagestips